Grinding wheel



March 14, 1939. E VAN DER PYL 2,150,886

GRINDING WHEEL Filed Sept. 23, 1937 EDWARD VANJJgR P'Yl.

Patented Mar. 14, 1939 GRINDING WHEEL Edward Van der Pyl, Holden, Mass,assignor to Norton Company, Worcester, Mass, a corporation ofMassachusetts Application September 23, 1937, Serial No. 165,367 6Claims. (Cl. 51-280) The invention relates to grinding wheels, and withregard to its more specific features to diamond grinding wheels.

One object of the invention is to provide a grinding wheel structureinvolving the use of a central disk and an abrasive rim or face in whichthe disk is an excellent heat conductor. Another object of the inventionis to provide a disk or center for a diamond grinding wheel which may beeffectively molded under the worst conditions of humidity andatmospheric heat. Another object of the invention is to provide acomposite Wheel having a non-grinding center of such characteristicsthat it can be effectively used to ream or lap a hole by thermalexpansion of the center.

Another object of the invention is to provide a composition for themanufacture of a wheel center of excellent characteristics for molding.Another object of the invention isto provide a com- 0 posite wheelhaving a non-abrasive center of exceedingly attractive appearance.Another object of the invention is to provide a center of the typeindicated of porous characteristics. Another object of the invention isto provide a cen- 25 ter of the type indicated of superior strength.Another object of the invention is to provide a center of excellentadhesive properties in connection with abrasive bearing resinoidmaterial.

Other objects will be in part obvious or in part 30 pointed outhereinafter.

In the accompanying drawing showing two of many possible embodiments ofthe mechanical features of my invention,

Figure 1 shows a cup-shaped wheel grinding 35 on one annular edgethereof, and

Figure 2 shows a disk-shaped wheel having an annular rim for peripheralgrinding.

Using the composition of matter hereinafter defined, and preferably withthe use of diamond 0 abrasive, I may manufacture grinding wheelsaccording to the method disclosed in Letters Patent to Baalis SanfordNo. 1,981,970. I provide a quantity of finely divided metal. This may bein the form of metal powders such as are used for 45 painting, but Iprefer a finely divided metal powder of a granular rather than a flakynature and of the type known as atomized metal powder.

I may also use finely divided electrolytic metal.

While, so far as certain features of the inven- 50 tion are concerned, Imay use many different metals, there are distinct advantages in the useof aluminum in'the practice of my invention. The ultimate grinding wheelshould be as light as possible in order that vibration on the spindle 55shall be reduced to a minimum. Furthermore,

I have found that the cost of the article when using aluminum isconsiderably less than when using certain other metal powders becausethe real .cost is a per volume cost rather than a per weight cost.Aluminum does not corrode rapidly 5 and, therefore, has distinctadvantages over the ferrous metals. The particle size of the aluminum ispreferably 100 mesh grit size and smaller.

I provide a quantity of resinoid, otherwise known as synthetic resin, inpowdered form. I prefer to use very finely divided resinoid powders ofthe order of 200 mesh or finer. I may use any commercially availableresinoid. For example, I may use and prefer to use a phenol-formaldehyderesin of the type sometimes referred to as Bakelite. However, myinvention may be readily practiced with the use of anyone of the alkydresins constituting the condensation product of a polyhedric alcoholwith a polybasic acid. Examples of these are the glyptal resin which isthe condensation product of glycerol with phthalic anhydride. Otheralkyd resins involving theme of other acids such as citric acid or theuse of other alcohols such as pentaerythritol may be used.

Instead of the polymerizable resins I may also use thermoplastic resinsor any one of the natural resins, such as shellac or the like. The termresin is, therefore, to be understood to cover both synthetic andnatural resins of varying types.

I take one part of the resin and ten parts of the aluminum by weight. Imay use as much as 25% by volume of the resin but I prefer to use alesser amount. I prefer to use at least 5% and 5 preferably more of theresin by volume.

The preferred proportion is, as stated, one part by weight of resin toten parts by weight of aluminum, which is the same as 14.8 parts byvolume of resin to 70 parts by volume of aluminum.

I take the designated proportions of powdered metal and powdered resin,for example aluminum and phenol-formaldehyde, and mix them thoroughly ina tumbling barrel. The mixing should be carried on until the powders arethoroughly mixed and the resin distributed throughout the mass ofaluminum powder. I provide a suitable mold having the shape of thegrinding wheel center to be manufactured. Referring now to Figure 1, Iprovide a cylindrical mold of the same size as the center I0. I place asuitable quantity of the mixture of resin and aluminum in the mold andpress the mixture with heat. I use a hot press which is heated to atemperature of in the neighborhood of 160 C. I maintain the heat at thistemperature for from flve to twenty-five minutes. I

I provide a volume of aluminum and resin as compared with the volume ofthe mold for the center l0 such that the center will have 15.2% ofpores. Thus the center l0 consists of a cylindrical disk with a centralhole II and comprises seventy parts by volume of aluminum, -14.8 partsby volume of resin and 15.2 parts of pore space. Characteristics of thisdisk are that it is extremely light and ductile, readily transmits heat,and will form a good adhesive union with a-mixture of abrasive grains.and resinoid. The porosity of the disk cannot be discerned with the eye.In fact, the disk appears to bea solid casting of aluminum.

Proceeding now according to the method clearly described in the patentto Sanford No 1,981,970, and having prepared a mixture of diamond grainsand resin, for example phenol-formaldehyde, and preferably the sameresin that is used for manufacture of the disk I 0, I mold a rim I! ofdiamonds bonded with resin around the disk l0. As described in thepatent referred to, the molding is preferably done in a hot press. Afterthe rim I2 is thus molded onto the disk It, I may place the grindingwheel l3 thus formed in an oven for further ciu'ing. Such further curingnot only cures the resin in the rim portion II but also in the diskportion ill.

I do not wish to be limited to the details of curing the resin in thedisk portion III or in the rim portion I2. I may initially cure theresin of the disk portion M for a much longer period than twenty-fiveminutes, for example for many hours. The thermo-irreversibility of thedisk III will depend, in the first place, upon whether athermo-irreversible polymerizable resin is used, and in the secondplace, upon the temperature and time involved ,in curing. These mattersmay be variedin accordance withknown experience and knowledge thereon.I'have found that after only a short time in the hot press, the disk IIIhas cohesion enough to hold together under further handling.

By providing suitable molds, I may readily form the wheel I of Figure 2.This wheel comprises a center I! which is cup-shaped and which comprisesresin plus metal as hereinbefore defined. A face IQ of resin bondedabrasive material, preferably diamonds, is molded onto the center I5under heat and pressure. This wheel likewise has .a central hole l1 andaplurality of small countersunk holes l8. The hole I! facilitatesmounting the wheel upon a spindle and the holes l8 serve to attach thewheel to a flange for driving purposes.

By reason of the porosity of the disks I 0 and I5, curing is readilyaccomplished since gases formed, for example ammonia and water vapor,readily pass ofl. It is found that the centers l0 and i5 can be readilystripped from the molds as they have a low coeillcient of friction.

A particular advantage of wheels made according to the invention is thatthey may expand and contract under heat and pressure without separa tionof the abrasive rimfrom the disk or center and without cracking of .anypart of the wheel.

- and center i5 constitute mounting portions of the 'wheel. Many shapesand arrangements other than those shown may be adopted in a wheel oftwo-part construction. The diamond abrasive rim I! or face i 6 is mosteffectively used and when it has been completely used up, the center ordisk may be discarded or, in case a thermoplastic resin was used, it maybe broken up and remolded.

It will thus be seen that there has been provided by this invention anarticle in which the various objects hereinabove set forth together withmany thoroughly practical advantages are successfully achieved. Asvarious possible embodiments might be made of the mechanical features ofthe above invention and as the art herein described might be varied invarious parts, all without departing from the scope of the invention, itis to be understood that all matter hereinbefore set forth or shown inthe accompanying drawings is to be interpreted as illustrative and notin a limiting sense.

I claim:

1. A grinding wheel consisting solely of a grinding portion comprisingdiamonds bonded with resin and amounting molded solely. from finelydivided metal and resin, the resin being 25% by volume or less ofthe-mounting.

2. A grinding wheel comprising a mounting consisting solely of aluminumgrain bonded with resin and a grinding portion of diamond grain bondedwith resin, the mounting and the grinding portion being integrallymolded together.

3. A grinding wheel comprising a mounting consisting solely of finelydivided metal bonded with resin and a grinding portion of diamond grainbonded with resin, the mounting and the grinding portion beingintegrally molded together.

4. A grinding wheel comprising a mounting consisting solely of aluminumgrain bonded with resin and a grinding portion of abrasive grain bondedwith resin, the mounting and the grinding portion being integrallymolded together.

5. A grinding wheel comprising a mounting of a composition consistingsolely of metal powder bonded with resin, there being not more than 25%by volume of the resin, and a grinding .portion consisting solely ofabrasive grain bonded with resin, the mounting and the grinding portionbeing integrally molded together.

6. A grinding wheel comprising a center mounting consisting solely ofmetal particles 'mixed with resin and a grinding portion comprisingabrasive grains bonded together, the entire wheel including the mountingbeing an integral piece, and the amount of resin in the mounting portionbeing not greater than 25% by volume.

EDWARD VAN nan PYL

